[FFmpeg-devel] [PATCH 2/4] avformat/avio: Limit url option parsing to the documented cases

[Michael Niedermayer]

From: Michael Niedermayer <michael at niedermayer.cc>

This feature is not know much or used much AFAIK, and it might be helpfull in
exploits.
No specific case is known where it can be used in an exploit though
subsequent commits depend on this commit though

Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
---
 libavformat/avio.c |   11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/libavformat/avio.c b/libavformat/avio.c
index 21713d9..05d0557 100644
--- a/libavformat/avio.c
+++ b/libavformat/avio.c
@@ -156,9 +156,16 @@ static int url_alloc_for_protocol(URLContext **puc, struct URLProtocol *up,
                 char sep= *++p;
                 char *key, *val;
                 p++;
+
+                if (strcmp(up->name, "subfile"))
+                    ret = AVERROR(EINVAL);
+
                 while(ret >= 0 && (key= strchr(p, sep)) && p<key && (val = strchr(key+1, sep))){
                     *val= *key= 0;
-                    ret= av_opt_set(uc->priv_data, p, key+1, 0);
+                    if (strcmp(p, "start") && strcmp(p, "end")) {
+                        ret = AVERROR_OPTION_NOT_FOUND;
+                    } else
+                        ret= av_opt_set(uc->priv_data, p, key+1, 0);
                     if (ret == AVERROR_OPTION_NOT_FOUND)
                         av_log(uc, AV_LOG_ERROR, "Key '%s' not found.\n", p);
                     *val= *key= sep;
@@ -243,7 +250,7 @@ static struct URLProtocol *url_find_protocol(const char *filename)
     size_t proto_len = strspn(filename, URL_SCHEME_CHARS);
 
     if (filename[proto_len] != ':' &&
-        (filename[proto_len] != ',' || !strchr(filename + proto_len + 1, ':')) ||
+        (strncmp(filename, "subfile,", 8) || !strchr(filename + proto_len + 1, ':')) ||
         is_dos_path(filename))
         strcpy(proto_str, "file");
     else
-- 
1.7.9.5